In oil and gas field operations, downhole measurements of various physical, chemical, and other parameters are routinely taken to monitor completion, stimulation, and production processes. Many conventional downhole sensors are either deployed permanently on casing in the annular space around the borehole casing or on tubing in the annular space inside the casing, or temporarily using retrievable means of conveyance such as wireline, slickline, or coiled tubing. Wireline logging and similar methods that employ retrievable sensor devices are useful to measure borehole and formation properties in between various completion, stimulation, and production processes, but would interfere with many of these processes (e.g., fracking) if used simultaneously therewith, which severely limits their utility for monitoring these processes in real time. Permanently installed sensors are not subject to this limitation, but pose other challenges. Permanently installed sensors may communicate with the surface via electrical, hydraulic, or optical fiber cables, or using some other transmission method, like low-speed communication with pressure pulses. They are commonly deployed on eccentric mechanical mandrels, and have an outer diameter (OD) that may be in the range between 0.75″ and 1.5″, and the sensors are commonly deployed on mechanical mandrels that are eccentric. This tends to require a larger clearance between the casing and the formation for casing-deployed single or multi-point sensors, or similarly a larger clearance between the tubing and casing for tubing-deployed single point or multi-point sensors. Since the cost of drilling a well is closely related to the size of the well, it may be desirable to minimize the size of the annular clearance needed. Optical fiber cables, which have a smaller outer diameter (e.g., between ⅛″ and ¼″) and therefore a smaller foot print than point sensors outside the casing, provide a beneficial alternative for certain types of measurements, such as temperature and acoustic measurements using distributed temperature sensing or distributed acoustic sensing techniques. However, the number and types of parameters that can be monitored directly with distributed optical fibers are limited. Accordingly, there is a need for alternative sensing systems and techniques, in particular, for means of measuring multiple downhole parameters and communicating them in real time to the surface while minimizing the size of the borehole to be drilled.